Various forms of carbons are well-known and have been used as pigments, sources of coke, chemical absorbers, etc. One type of carbon forms through the disproportionation of carbon monoxide in the presence of a ferrous group metal. As used herein, "disproportionation" means any of the reactions which occur in the presence of a ferrous group metal to produce carbon from a carbon monoxide containing gas, which may also contain hydrogen and other substances. The following are typical reactions: ##STR1##
In the past, the carbon formed by disproportionation has had little commercial value. In many chemical processes, such as processes involving the Fischer-Tropsch synthesis, the formation of such carbon through disproportionation is an undesirable side reaction and may even deactivate the catalyst used in such processes due to carbon deposition on the catalyst.
It is known that carbon will react with hydrogen to form methane (CH.sub.4), the main ingredient of natural gas. But the known carbons have such a slow reaction rate at temperatures where high methane concentrations are thermodynamically allowable that experts consider a commercial process to produce methane based on this reaction as unfeasible. Demand for methane has, however, increased and almost outstripped the supply. Consequently, a process to synthesize methane would be of great benefit to the economy.
It has been proposed that methane may be produced from coal, and, consequently, extensive research is being conducted to find economical ways to convert coal into methane. For example, methane has been made from a synthesis gas of carbon monoxide and hydrogen produced by burning coal in a mixture of oxygen and steam. Oxygen is used rather than air so that the synthesis gas will not contain substantial amounts of nitrogen, a major ingredient of air, because nitrogen cannot be readily separated from the synthesis gas or the methane product. One disadvantage of this process is that costly oxygen plants are required. Moreover, the carbon dioxide produced in the premethanation steps of the process is removed from the carbon monoxide-hydrogen feed stream. This involves a relatively expensive gas separation step.